1. Field of the Invention
The present invention relates to an image forming apparatus such as a color laser printer.
2. Prior Art
Conventionally, as an electrophotographic laser printer, a tandem color laser printer is known, which includes four photosensitive drums to correspond to toners for four colors: yellow, magenta, cyan, and black.
A tandem color laser printer, which forms the toner image of each color on the corresponding each photosensitive drum at substantially the same time, can form color images as fast as a black and white laser printer can.
For example, in a known tandem color laser printer, one drum drive motor drives four photosensitive drums via a reduction gear, a drum drive gear, and a drum gear (see Japanese Unexamined Patent Publication No. 09-179372, for example).
Alternatively, a tandem color laser printer is known in which four drum drive motors are provided to correspond to four photosensitive drums and each drum drive motor drives each photosensitive drum (see Japanese Unexamined Patent Publication No. 2001-281959, for example).
Alternatively, in a known tandem color laser printer, a Bk motor for driving one photosensitive drum corresponding to black, and a YMC motor for driving three photosensitive drums corresponding to yellow, magenta, and cyan are provided. The Bk motor drives one photosensitive drum corresponding to black and at the same time the YMC motor drives three photosensitive drums corresponding to yellow, magenta, and cyan (see Japanese Unexamined Patent Publication No. 2005-157098, for example).